The present invention relates to bag structure and particularly thin wall bags fabricated from thermoplastic materials such as polyolefins, including polyethylene and polypropylene. The bags of the present invention are characterized by having an integral closure feature whereby when it is desired to close the open mouth of the bag the mouth is merely gathered together, twisted, and released. The bag mouth retains its closed, twisted configuration without the employment of extraneous fastening devices.
In the past, thin walled thermoplastic bags were usually closed by gathering the top end of the bag over the contents, twisting the gathered end and tying the twisted neck of the bag for example, with a rubber band or a length of paper coated wire commonly referred to as a twist-tie. Such closing means are often supplied by the bag manufacturer as a separate item in the package of bags. These closures have a common characteristic, i.e., they are separate from the bag so that frequently they are not at hand when needed. U.S. Pat. No. 3,402,052 discloses the employment of strips of metallic foil which are adhered along the entire length of bread overwrap material so that, after opening, the bread package may be reclosed by twisting the neck of the wrapper closed. The twisted end of the package, by virtue of the dead-fold characteristics of the metallic foil, remains closed until it is desired to reopen the package by untwisting the package end. Such a closure arrangement requires a considerable amount of metallic foil, a relatively expensive commodity, to function effectively.